The present invention relates to a signal transmitting device and a signal transmitting method, and more particularly to a compensator for reducing harmonic distortion tones of a signal transmitting device, and a method thereof.
In the field of wireless communication systems, a transmitter may consume most of the power of the front end circuit. A high efficiency transmitter is therefore required. In the high efficiency transmitter, a passive mixer is usually adopted since the passive mixer consumes less current and occupies a smaller silicon area than other mixers. The passive mixer will produce LO (Local Oscillator) harmonics terms at the input of the driver of the transmitter. These LO harmonic terms will be intermodulated with the desired signal, which produces distortion terms at the output of the driver. These distortion terms will degrade aspects of the transmitter performance such as EVM (Error Vector Magnitude), spectral emission, etc. The transmitter performance may also be degraded by the IF (Intermediate Frequency) nonlinearity effect, which causes the transmitter to produce distortion terms at the mixer input. Therefore, how to reduce the distortion terms generated by either IF nonlinearity or the intermodulation terms between LO harmonics and the desired signal of a transmitter is an urgent problem in this field.